1. Field of the Invention
The present invention relates to a junction box for connecting and branching the terminals of wire harnesses or electrical units on automobiles or the like, and a process of assembling such a junction box.
2. Description of the Prior Art
Complicated wiring of the electrical circuit in a vehicle such as an automobile, is readily completed by connecting the terminals of electrical units and wire harnesses to external connectors formed in the insulating case of a junction box formed by properly arranging conductors interconnecting the electric contacts in the insulating case. As such a junction box in general is disposed in the engine room, the junction box is often exposed to oil and water as well as to high temperature. Particularly, when the engine room is washed with a spout of high-pressure water, it is possible that water intrudes into the junction box even if the same is covered with a watertight cover. Accordingly, the insulation of the junction box is reinforced by filling voids within the insulating housing with a thermosetting resin such as an epoxy resin, and hardening the resin after placing wiring boards carrying conductors in the insulating case so as to enclose the wiring boards with the resin.
However, since the connector bodies of the junction box for receiving external connectors are formed in the upper and lower surfaces of the insulating case in the junction box, and the electric contacts thereof are connected to the conductors and penetrating through the upper and lower surfaces are arranged in the connector bodies, the connecting function of the contacts will be spoiled if the resin fulled in the insulating case leaks out through the through holes through which the contacts are projecting and adheres to the contacts. To prevent the leakage of the resin from the insulating housing through gaps between the contacts and the through holes due to the excessive filling of the resin in the housing and or due to the expansion of the resin filled in the housing, packings need to be attached scrupulously to the housing and the exact amount of the resin needs to be filled in the housing. Furthermore, a long time required for hardening the resin affects adversely to the productivity of the process for manufacturing such a junction box.
On the other hand, as illustrated in FIG. 10, to arrange the contacts b accurately in a connector body formed in the bottom cover c on its outer surface, a packing for preventing the leakage of the resin is attached to the backside of the cover c, then the wiring plate pile a is joined to the cover c by inserting contacts b through holes h formed in an accurate arrangement in the cover c, then the assembling of the cover c and the wiring plate pile a is placed in an insulating housing which is then filled with a thermosetting resin, in which the filled resin is hardened by heating. However, such a junction box includes many parts and requires many assembling processes, scrupulous work in assembling the parts without allowing the resin to leak, and a long time for hardening the resin, which affects adversely to the productivity of the manufacturing process.
To solve such problems in the conventional junction boxes, the inventors of the present invention have previously proposed a process of assembling a junction box comprising steps of embedding a pile of a plurality of insulating plates in an insulating resin to form a wiring board assembly, and mounting the wiring board assembly in an insulating housing. Such an assembling process improves the insulation between the conductors within the insulating housing, whereas the watertightness between the contacts and the housing is not necessarily improved and the problem of current leak between the contacts cannot be solved. Furthermore, such an assembling process requires to form the insulating plate pile and the insulating housing in a paricularly high dimensional accuracy, and the positioning error even in a single part make assembling the junction box impossible.